Influences on Metal Support to Mine Transient Electromagnetic Detection and Correction Technology

In order to eliminate the influence of metal support on the distribution of electromagnetic field and avoid misjudgment during roadway TEM detection, the finite difference equations with thin metal layer were deduced in this paper according to the Maxwell equations and finite difference principle. Based on the deduced eq uations, the whole space transient electromagnetic response curves were calculated by using non- uniform grid under conditions of different metal layer thickness, then a correction coefficient was given to correct the influence of metal support. It turned out that the apparent resistivity values without the effect of metal layer varies from 15 Q.m to 4 Q.m along the detection direction, but under the effects of metal layer, low resistivity of about 3 Q:m exists in the deep region besides the same trend as ab ove case. After the correction, the low resistivity region was disappear, and this result was verified by the drilling. The correction technology proposed in this paper was an effective method to eliminate the metal support influence in roadways, and avoid false anomaly generated in the mine transient electromagnetic detecting.